Well for a futuristic game I find no problem with the scope. Just the stock. Maybe bring the stock down to where the thing that connects to the pistol grip. Looks like if you brough it down to there just sort of tilting the back down it would straighten the top out, and stil look like the same weapon.
As Scopes do vary greatly in length depending on their power. Those M-16 scopes are only 4x where my rifle scope on my Remington PSS 700 is 6-20.
Also it's very tubish but then again futuristic. Real scopes have wider lenses in the front to help gather more light in low light situations. Where the little 4x scopes are very poor at doing that.
I know I have one on a SKS and if it's not mid day it's pretty dim. On a note though I'm really diggin' the hover bike! Especially the dual exhaust, and the guy too.
As noted above about a windshield if I was going to add one I'd make it look more like a HUD display. Or leave it as is windshields are for old men anyway lol.
Of course a couple of other ideas. First I might sweep that mag forward just a hair. Although it looks good now. Then I would clip the bottom of the mag slap off. No offense but it's too big. It should be thin like just a metal plate with some overhang on the front.
Also the side cuts are pretty standard mag stuff. If you wanted a more exotic look you could make it resemble a waffle mag. Do a search for AK-47's and you should catch some pictures of waffle mags. Instead of having vertical grooves they have like waffle ridges running horizontal across them.
The mag looks nice the way it is though. Just offering idea's. Waffle mag's are sought after by shooters though because they're nearly indestructable, and allow for a great grip no matter if they're covered in mud or your wearing gloves.
Also for some eye candy when you texture be sure not to use the same texture for the mag as you do for the rifle. Mag's typically aren't made by the gun manufacturers and go through a different coating process. They also tend to see twice the abuse and neglect a weapon does.
Maybe sweep that pistol grip back a hair for a more ergonomic look.
Like I said all just what I would do. It all looks good just the stock position bothered me. I have to give you credit for your creativity. I can model just about anything that I can see. However it's only certain times when I can just dream up a creation.
He who stands on toilet is high on pot!